Quantum-like approaches for robust photonics

Germano Montemezzani

Michel Boyer, Tal Mor

Quantum Key Distribution (QKD) with classical Bob has recently been suggested and proven robust. Following this work, QKD with classical Alice was also suggested and proven robust. The above protocols are ideal in the sense that they make use of qubits. However, in the past, well-known QKD protocols that were proven robust and even proven unconditionally secure, when qubits are used, were found to be totally insecure when photons are used. This is due to sensitivity to photon losses (e.g., Bennett's two-state protocol) or sensitivity to losses combined with multi-photon states (e.g., the photon-number-splitting attack on the weak-pulse Bennett-Brassard protocol, BB84). Here we prove that QKD with classical Alice is still robust when photon losses and even multi-photon states are taken into account.

Thomas P. Pearsall

Yusuf Karli, René Schwarz, Florian Kappe +11 more

The generation of single photons using solid-state quantum emitters is pivotal for advancing photonic quantum technologies, particularly in quantum communication. As the field continuously advances toward practical use cases and beyond shielded laboratory environments, specific demands are placed on the robustness of quantum light sources during operation. In this context, the robustness of the quantum light generation process against intrinsic and extrinsic effects is a major challenge. Here, we present a robust scheme for the coherent generation of indistinguishable single-photon states with very low photon number coherence using a three-level system in a semiconductor quantum dot. Our approach combines the advantages of adiabatic rapid passage and stimulated two-photon excitation. We demonstrate robust quantum light generation while maintaining the prime quantum-optical quality of the emitted light state. Moreover, we highlight the immediate advantages of the implementation of various quantum cryptographic protocols.

Sunil Mittal, Venkata Vikram Orre, Mohammad Hafezi

We theoretically study the transport of time-bin entangled photon pairs in a two-dimensional topological photonic system of coupled ring resonators. This system implements the integer quantum Hall model using a synthetic gauge field and exhibits topologically robust edge states. We show that the transport through edge states preserves temporal correlations of entangled photons whereas bulk transport does not preserve these correlations and can lead to significant unwanted temporal bunching or anti-bunching of photons. We study the effect of disorder on the quantum transport properties; while the edge transport remains robust, bulk transport is very susceptible, and in the limit of strong disorder, bulk states become localized. We show that this localization is manifested as an enhanced bunching/anti-bunching of photons. This topologically robust transport of correlations through edge states could enable robust on-chip quantum communication channels and delay lines for information encoded in temporal correlations of photons.

Thomas P. Pearsall